Process for coking oil



Aug. 28, 1934. A. FISHR 1,971,906

' PRocEss FOR COKING OIL A Filed Oct. 2, 1931 ATTORNE aan@ Aug. 28, 19a i *o 1,971,906

PROCESS FOR. COKING OILA Alfred Fisher, Chicago, lll., assignor to Universal Oil Products Company, Chicago, lll., a corporation of South Dakota Application october 2, 1931, serial No. 566,53

6 Claims. (ol. 2oz- 5) This invention relates to the treatment of hyof steam or water onto its surface, removing from drocarbon oils and more particularly refers to the the zone of treatment the loose carbonaceous maheat treatment of oils, such as petroleum and its terial which accumulates in the retort. residues, coal tars, pitches and the like to substan- I have found that by cooling the coke or cartially devolatilize the same and effect their rebonaceous layer upon the walls of the retort by the duction to coke or carbonaceous material. introduction of water or steam onto its surface,

Many processes for continuously coking hydrosaid carbonaceous mass contracts more rapidly carbon oils have been proposed, some of which than the shell of the retort, thus breaking the utilize indirect heating of the material to be bond therebetween and effecting removal of the coked while others employ direct contact between carbonaceous layer. I have also found that by 85 said material and the heating medium. One this method of removing the coke which adheres process of the former class employs a plurality of to the walls of the retort it normally falls away in chambers which may be externally heated or to relatively large pieces, thus minimizing the prowhich the material to be coked is supplied in a duction of small coke particles or fines which preheated state,.one of which chambers is being filled dominate in many other methods of coke re- 70 with coke while the others are being cleaned and moval. prepared for operation. This method involves It is also characteristic of the operation of the costly and cumbersome equipment and is also present process that the temperature in the coking hazardous, due to the relatively large volume of zone need be reduced only sufficiently to break combustible material which is ordinarily mainaway the adhering carbonaceous mass from the 75 tained in the. coking zone. walls of the retort after which the coking opera- Other processes of the same type employ metion may be continued, the total coke-removing chanically operated scrapers or other means of period consuming only approximately 15%, or in loosening the carbonaceous material from the some cases somewhat more, of the total operating walls of the coking vessel, continuously introductime. 80

ing oil to the heated zone and continuously remov- The attached drawing illustrates diagrammatiing coke or carbonaceous material from the syscally in vertical section one specic form of appatem. Eiiicient apparatus f or such operations have ratus in which the process of the present invennot so far been developed, the chief obstacle betion may be accomplished. The drawing and the ing warping or distortion of the scrapers or other following description are given for the purpose 85 coke-removing devices, due to the high temof more clearly illustrating the novelty and feaperatures employed and inability to properly cool tures of the invention. The rotary retort is indithe apparatus. Methods of the type involving cated in general at 1. The cylindrical shell 2 of direct contact of the material to be coked with the retort is located in a suitable furnace setting 3 heating mediums such as products of combustion and is rotated by any suitable motivating means; 90 and other processes involving partial combustion (not shown) through gear arrangement 4. Ends of the materials undergoing coking are objection- 5 and 6 of the retort, located outside the heating able, regardless of the methods used to remove zone of the furnace preferably are stationary and the coke from the zone of treatment and thus any suitable form of packing arrangement (not operate the process continuously, on account of shown) is provided ybetween the rotary shell 2vr 95 the objectionable oxidation products formed, loss and stationary ends 5 and 6 to prevent escape of of material due to oxidation or combustion and materials from the retort. y

inability to eciently separate hydrocarbon `Any suitable fuel such as oil, gas, pulverized vapors from combustion products. solid fuel or the like is supplied to combustion The present invention offers distinct improvezone 7 of the furnace by means of any suitablev` 100 ments to the existing art by providing a method burner (not shown)l through burner port 8, The and means of intermittent operation whereby hyhot combustion gases pass upward through the drocarbon oils such aspetroleum and its residues, perforated arch .9 of the furnace, along shell 2 coal tars, pitches and the like or mixtures of such of the rotort through heating zone l0 and out of oils are reduced to coke or carbonaceous matethe furnace to a suitable stack (not shown) 105 rial by treatment in an externally heated rotary through flue opening 11. retort.' The most essential improvement of the r`The retort is provided with any suitable feeding present invention comprises intermittently ararrangement such as, for example, a perforated resting the coking operation and cooling the carfeedpipe 12 traversing the length of the retort bonaceous mass in the retort by the introduction into which the material to be coked is introduced 110 through line 13 and valve 14 to be sprayed onto lthe heated walls of the retort through suitable perforations 15. Preferably, the size and spacing of perforations 15 are such that a substantially uniform quantity of charging material is supplied to all portions of the inner surface of shell 2. By rotation of shell 2 it is substantially uniformly heated around its entire circumference and by such heating the material sprayed against the walls of shell 2 is substantially devolatilized and reduced to coke or carbonaceous residue.

Preferably the form and size of perforations 15 is such that the charging material is sprayed against the walls of the retort in a somewhat atomized form and, to prevent plugging of perforations l5, steam may be intermittently supplied to charging line 12 through line 16 and valve 17, the flow of oil through valve 14 preferably being stopped during said intermittent steaming operations.

Asa layer of coke or carbonaceous material builds up upon the inner surface of shell 2, the poor heat conductivity of the carbonaceous material will reduce the flow of heat from the furnace to the material undergoing coking. To offset this reduction in the rate of heat transfer the furnace temperature preferably is gradually increased during the coking operation. The heated shell 2 of the retort is preferably constructed of a suitable metallic alloy such as nickel chromium steel capable of withstanding the relatively high temperatures to which the shell of the retort is subjected.

After a substantial layer of coke has been built up upon the inner surface of revolving shell 2 of the retort the supply of charging stock to the zone of treatment is stopped. Preferably, heating of the retort is continued for a time after the feed is discontinued to substantially vaporize any vola-- tile matter remaining on the surface of the coke layer. Firing is then discontinued or substantially diminished and water or steam introduced to feed line 12 through line 16 and valve 17 is sprayed through perforations 15 upon the surface of the bed of coke, the rotation of the retort being preferably continued during this operation. By this method the coke is cooled and contracts more rapidly than shell 2 of the retort, thus breaking the bond between the metal shell and the carbonaceous layer. Thefcoke cracks and scales vaway from the Walls of the retort in relatively large pieces and passes to the discharge end 6 of the retort, assisted by the continued rotation of shell 2 and the slight inclination of the retort from the horizontaltoward its discharge end 6. The stationary discharge end of the retort is provided with a coke discharge tube 18 and an outlet line 21, containing valve 22, for vapors and gases. The lower end of coke discharge tube 18 is preferably immersed in lliquid which acts as a seal to prevent the escape of vapors and gases through this port.

Any suitable liquid, such as oil or water, may be employed, and may serve also as a quenching medium for the coke. Coke may be discharged during the intermittent cleaning operation of the retort into a continuous conveyor 19 of any suitable form, one end of which is immersed in the liquid seal and quenching chamber 20 and by means of which the coke may be removed to storage or elsewhere, as desired. Vapors removed from the retort through line 21 and valve 22 may pass to fractionation, condensation,lcooling and collection apparatus or to any other desired treatment, means for which are well known and are tially atmospheric pressure although relatively low superatmospheric pressures or partial vacuum may be employed, if desired. Coking temperatures employed, i. e., temperatures to which the oil is subjected during the coking operation, may range from 900 to 1300 F., more or less, depending primarily upon the type of material being treated and the desired volatility of the coke produced as well as the desired characteristics of the other products of the process. Preferably, the temperature of the carbonaceous mass is reduced by from 300 to 600 F., more or less, by spraying it with Water or steam during the scaling or cokeremoving period of the operation.

As a specific example of the operation of the process of the present invention, a residual oil resulting from cracking, which contains about 23.7% of coke by laboratory distillation analysis, is supplied to the externally heated rotary retort at a rate of about 1500 pounds per hour. The furnace temperature, i. e., the temperature measured in the heating zone of the furnace adjacent to but outside of the rotary shell of the retort, is about 1200"' F. when the feed of oil to the retort is started'and is increased over about a four hour period to approximately 1800 F. This temperature is then maintained for about four hours, during which time the feed rate is gradually decreased from approximately 1500 to about 500 pounds of oil per hour. During'this eight hour period the oil is continuously sprayed into the coking zone for approximately 10 minutes and the 10 minute charging periods are interrupted by about one-half minute periods during which steam is passed through the perforations in the charging line to prevent their plugging.

After about eight hours of operation the supply of oil to the retort is stopped and firing is continued for approximately 20 minutes after which the fires are diminished, but not entirely extinguished, and water is sprayed onto the surface of the layer of carbonaceous material which has accumulated on the shell of the retort. In this manner the temperature in the retort is reduced by about 400 F. over a period of approximately one hour, during which time substantially all of the coke or carbonaceous material will have scaled away from the walls of the retort, being removed from the discharge end thereof. The injection of water is then stopped, the firing is increased and charging of oil to the retort is resumed at the rate of approximately 1500 pounds per hour and the operation progresses substantially the same as before. The evolved vapors and gases are continuously withdrawn from'the discharge end of the retort during the coking operation to condensation, cooling and collection apparatus and during the cooling and cleaning operation steam and other gases from the retort are Wasted.

An operation such as above outlined may yield about 18% of petroleum coke having a volatile content of less than 5%. The total liquid recovered from such an operation may be '75% to 80% of the total charge, 20% to 25% being chargeable to gas and operating loss. In this manner the cracked residual oil is substantially freed of carbonaceous material and bythe same operation a gas of high ealoriflc value and a carbonaceous fuel are produced.

It will be understood that the operation above outlined is given only for the purpose of illustration. It is only one of the many operations possible with the process of the present invention and is not intended as a .limitation thereon.

The word water as used in the claims is intended to include water in liquid or in heated vaporous form.

I claim as my invention: n

1. A continuous process for coking hydrocarbon oil, which comprises feeding hydrocarbon oil to be cracked into an externally heated rotating retort where it is subjected to a temperature sufliciently high to reduce said oil to coke, introducing steam into said retort whereby clogging of said oil feed is prevented, intermittently interrupting said oil feed and feeding water to said retort whereby to loosen and dislodge coke formed on the wall of said retort, removing said dislodged coke, and separately removing any vapors volatilizing in said retort.

2. A process for the continuous coking of hy drocarbon oil, which comprises feeding hydrocarbon oil to an externally heated rotating retort, introducing steam into said retort whereby cloggingof said oil feed is prevented, subjecting said oil to a temperature suiliciently high to reduce same to coke, intermittently interrupting the feed of oil to said retort and during said period of interrupted feed of oil, feeding water to said retort whereby to dislodge coke accumulated on the inner wall of said retort, removing said dislodged coke from the retort, and separately removing vapors from said retort. 1

3. A process for the continuous coking of hydrocarbon oil, which comprises feedingl hydrocarbon oil to be cracked into a rotating retort, introducing steam into said retort whereby clogging of said oil feed is prevented, externally heating said retort whereby said oil is raised to a temperature at which it is reduced to. coke, interrupting the feed ofl said oil and in its stead feeding water to said retort to dislodge the coke accumulated on the inner wall of said retort, removing said coke from said retort and collecting same, separately removing vapors volatilizing in said retort, and intermittently feeding oil and water to said retort without interrupting the rotation of said retort.

4. A process for coking hydrocarbon oil, which comprises feeding hydrocarbon oil upon the inner surface of a. rotating retort, externally heating the rotating retort, while feeding said hydrocarbon oil, to a temperature suillciently high to reduce said oil to coke, intermittently interrupting the feeding of said oil and feeding water to said retort to loosen and dislodge the coke formed on the wall of said retort, removing said dislodged coke from the retort, and separately removing vapors from said retort.

5. A process for coking hydrocarbon oil which comprises spraying hydrocarbon oil upon the inner surface of a rotating retort, and upon the surface of coke formed thereon, externally heating the rotating retort, while spraying said hydorcarbon oil, to a temperature sufficiently high to reduce said oil to coke, intermittently interrupting the feeding of said oil and spraying water upon the surface of the coke accumulated in the inner surface of the retort whereby to dislodge said coke, removing said dislodged coke from the retort, and separately removing vapors from said retort.

6. A continuous process for coking' hydrocarbon oil, which comprises, spraying said oil to the internal walls of an externally heated rotating retort whereby a film of coke is formed upon said walls, intermittently interrupting the feed of oil for a relatively short period and 'passing steam through said oil feed to prevent clogging of the same, intermittently interrupting the feed of oil for a relatively longer period, and spraying water upon the film ofcoke to dislodge the same from thewalls of the retort, and removing said dislodged coke and vapors from said retort.

ALFRED FISHER. 

